THIS IS A RUSH TRANSCRIPT. THIS COPY MAY NOT BE IN ITS FINAL FORM AND MAY BE UPDATED.

[18:00:01]

WOLF BLITZER, CNN ANCHOR: Happening now, breaking news: terrorist takedown, the most wanted man in Europe among five terror suspects arrested in Belgium, Salah Abdeslam, accused of playing a key role in the Paris terror attacks, wounded, but captured alive. What does he know about other attacks being plotted right now?

Romney repulsed. Mitt Romney launching a new effort to stop Donald Trump, announcing he will vote for Ted Cruz in the Utah caucuses next Tuesday and encouraging others to do the same thing. Romney also calling for a contested Trump. Would that prompt Trump and his millions of supporters to leave the GOP?

Walkout. Bernie Sanders walks out of a TV interview suddenly, apparently angered or a question about his wife. But he's forging ahead with his campaign, even as he falls farther behind Hillary Clinton in the delegate count. With poor prospects ahead, is he still planning to go all the way to the Democratic Convention?

And Cuban wonder. An American president heading to Cuba for the first time in almost a century, but ahead of the historic Obama trip, CNN's "WONDER LIST" visits this country at a crossroads. I will talk to the host, Bill Weir, about his remarkable journey later this hour.

We want to welcome our viewers in the United States and around the world. I'm Wolf Blitzer. You're in THE SITUATION ROOM.

ANNOUNCER: This is CNN breaking news.

BLITZER: We're following breaking news, the capture of the man believed to be the only terrorist to survive the Paris attacks. Salah Abdeslam, the most wanted man in Europe, wounded, but taken alive in a massive anti-terror operation in Brussels, he's believed to be the driver who dropped off suicide bombers at the French national stadium, one of multiple attacks that killed 130 people last November.

And there's other breaking political news we're following tonight. Mitt Romney announcing he will vote for Ted Cruz in next week's Utah caucuses and encouraging Republicans to do the same thing to stop Donald Trump from becoming the Republican nominee. Romney stopping short of a full endorsement of Cruz, but endorsing a brokered convention and slamming what he calls Trumpism as racist, bigoted, vulgar and more.

Our correspondents and expert analysts, they are all standing by.

But let's begin with the breaking terror news right now.

Our chief national security correspondent, Jim Sciutto, is working the story for us.

Jim, Salah Abdeslam, he had been on the run now for four months. Give us the latest.

JIM SCIUTTO, CNN CHIEF NATIONAL SECURITY CORRESPONDENT: Wolf, until just 48 hours ago, the trail for Salah Abdeslam had gone completely cold. Now tonight, he is in police custody, four other terror suspects as well. Both French and Belgian authorities declaring a major victory in their battle against terror.

(BEGIN VIDEOTAPE)

SCIUTTO (voice-over): Guns drawn, Belgian police stream down a street in Brussels searching for one of the most wanted men in the world. After an exchange of gunfire, Salah Abdeslam, the one surviving terrorist behind the deadly November Paris attacks, is wounded, but captured alive.

UNIDENTIFIED MALE: An ambulance has just arrived because there are two people who are in the apartment who are shot by the police and one apparently is Salah Abdeslam.

SCIUTTO: One terror suspect seen taken down by police here. It is unclear whether this is Abdeslam. The Belgian prime minister and French president together keeping close tabs, a crucial moment in Europe's fight against terror.

FRANCOIS HOLLANDE, FRENCH PRESIDENT (through translator): The Belgium and French intelligence services are cooperating on the investigation. This is an important moment, but we ought to let the Belgian police do their work without disturbance.

SCIUTTO: The arrest comes just two days after Abdeslam's fingerprints and DNA were found in another apartment raided by police, a lucky break in a manhunt that had gone cold for months.

In that raid, one suspect was killed, two others escaped, one possibly Abdeslam himself. Salah Abdeslam is the 10th ISIS terrorist behind the Paris attacks and the only one to escape alive from the deadliest terror attacks in Europe in more than a decade. Police nearly captured him during a traffic stop outside Paris just hours after the shootings, realizing who he was only after they let him go.

He then led authorities on a global hunt, extending from Belgium all the way to Syria, multiple allies involved, including the U.S.

JOSH EARNEST, WHITE HOUSE PRESS SECRETARY: The United States obviously has significant resources and significant capabilities and we have used them to assist the French and the Belgians. (END VIDEOTAPE)

SCIUTTO: Tonight, French and Belgian authorities very careful to say that the terror threat remains very high. In fact, we heard the French president say that one thing they discovered in these most recent raids is that the network behind the Paris attacks was bigger, much bigger than they knew before these last 48 hours.

[18:05:00]

And, Wolf, I spoke with the French interior minister just a few days ago. He said that the chances of another terror attack in France this year in 2016 is very high, in fact, in his words, likely.

BLITZER: Pretty disturbing. And U.S. intelligence officials have said they're worried about a terror attack here in the United States this year as well.

Let's bring in CNN's Brian Todd. He has more on Salah Abdeslam, his terror ties, his role in the Paris attacks.

Brian, what else are you learning?

BRIAN TODD, CNN CORRESPONDENT: Wolf, it's not clear just how long Salah Abdeslam has been affiliated with ISIS. But we do know he's got a criminal history and that he knew one of the key plotters in Paris for several years.

Abdeslam and Paris attack leader Abdelhamid Abaaoud were convicted in the same crime in Paris in 2010 and spent jail time together the following year. Salah Abdeslam is 26 years old. He was born in Belgium, but is a French national. His brother Brahim Abdeslam is believed to be one of the suicide bombers in Paris on November 13.

But Salah Abdeslam, even though he believed to have worn a suicide belt that night, is said to have had a more volatile temper than his brother. With all those things into consideration, he did not go through with an attack on November 13. He dropped off three suicide bombers at the Stade de France that night. Then he ditched his black Renault Clio and vanished.

Investigators say he either had a technical problem with a suicide belt or he simply chickened out that evening. The night of the attacks, he called two friends to pick him up. They whisked him away from Paris and got him into Brussels, where he melted away and was able to hide for four months with some help, Wolf. Today, a major breakthrough.

BLITZER: But there were two other earlier occasions when Abdeslam was almost caught? Is that right?

TODD: That's right. On the night of the Paris attacks, just hours after the shootings, he and friends were driving back from Paris toward Brussels. He called two friends to pick him up. They drove him from Paris to Brussels. But in that drive, they passed through at least two checkpoints. But

at that time, police had not established that he was a suspect in the Paris attacks. They let him go on his way. Then, just three days ago, there was another raid on another Brussels apartment. Wolf, authorities found Abdeslam's fingerprints and his DNA in that apartment.

But he had slipped away there. A Belgian sniper shot and killed another operative who was said to have helped him. That particular operative was said to have directed the Paris attacks from a remote phone on the night of the Paris attacks from Belgium, so very significant operations this week to get Abdeslam tonight and to kill that other operative on Tuesday night.

BLITZER: Yes, 26 years old, supposedly a true ISIS believer. The question is, will he now talk to law enforcement or will he remain silent?

TODD: That's right. That's going to be a key thing.

And there are -- there is evidence that there are other plotters out there who were involved in the Paris attacks and that they have a wider network throughout Europe. There are operatives out there on European soil. You just heard Jim talk about possible attacks coming in Paris and elsewhere this year.

Salah Abdeslam could some have key information to maybe lead authorities to intercept some of those attacks.

BLITZER: All right, Brian Todd, thanks very much. We're going to have more on this story, the breaking news, coming up.

But there's other breaking news coming up, political news, a dramatic new effort by Mitt Romney to stop Donald Trump from winning the Republican presidential nomination. In a Facebook post, Romney says he's voting for Ted Cruz in next Tuesday's Utah caucuses. And he's calling for others to do the same thing to prevent Donald Trump from getting the delegates he needs to win outright and forcing a brokered Republican Convention.

Romney goes on to write -- and I'm quoting now -- "Through the calculated statements of its leader, Trumpism has become associated with racism, misogyny, bigotry, xenophobia, vulgarity and most recently threats and violence," Romney adding, "I am repulsed by each and every one of these."

CNN's Sunlen Serfaty is joining us now from Phoenix with the latest.

What can you tell us, Sunlen?

SUNLEN SERFATY, CNN NATIONAL CORRESPONDENT: Well, the Cruz campaign, Wolf, obviously thrilled with this news that Romney will vote for Ted Cruz.

The Cruz campaign immediately tweeting out from its official account, "Thank you, Governor." And a Cruz campaign official telling me: We agree with Mitt Romney. If people want a conservative Republican to win the nomination, they should vote for Ted Cruz.

Now, Cruz spent most of the morning today and the afternoon today in a town called Douglas, Arizona. That's right on the border with Mexico obviously talking about the problem of illegal immigration, but of course he was pestered with questions about this statement from Mitt Romney today.

He said: "I very much appreciate the fact that Romney announced that he will vote for me, and I'm really happy that he encouraged others to do the same." But of course he was pressed that Mitt Romney fell short of a full-fledged endorsement, rather almost endorsing the idea of strategically voting in Utah and other states to prevent Donald Trump from going forward, really endorsing the idea more so of a contested convention.

So, interesting response there from Ted Cruz today. Now, Cruz will be campaigning in Mitt Romney's state of Utah tomorrow. Unclear whether they will appear together. I asked the Cruz campaign moments ago if that will happen. They say it still hasn't been decided yet -- Wolf.

[18:10:10]

BLITZER: Do they think, the Cruz campaign folks, that Cruz will win either Utah or Arizona on Tuesday?

SERFATY: Well, they are really downplaying expectations in Arizona, Wolf. They say that Donald Trump is so far ahead in the early vote that they are trying.

But, of course, they are trying to make inroads there, spending a good amount of time today really investing. They think they could come from behind there. They liken that to what they saw in Louisiana, the last-minute vote really turning towards them. In Utah, they are really going full-fledged.

We heard Ted Cruz really say that he's got a good shot at winning all of the delegates in Utah. Of course, he made this sort of pressured pitch for John Kasich's supporters to come on his side, saying every vote for John Kasich in Utah is a vote essentially for Donald Trump.

BLITZER: All right, Sunlen, thanks very much.

We are going to continue to follow this story, a lot more on the breaking political news, much more on the terror news coming out of Brussels, Belgium, as well. Let's take a quick break. We will be right back.

(COMMERCIAL BREAK)

[18:15:26]

BLITZER: We're following two big breaking stories this hour. Stand by for more on Mitt Romney's dramatic decision to back Ted Cruz in the Utah Republican caucuses.

But I want to go back to the other breaking news we're following, the news in the war on ISIS, a key suspect in the Paris terror attacks captured in Brussels today after a four-month manhunt. Salah Abdeslam is believed to be the only terrorist who survived the attacks that left 130 people dead, many of them young children and teenagers. He was shot in the leg before being apprehended. But he's alive tonight and facing extradition to France.

We're back with the ranking member of the House Intelligence Committee, Democratic Congressman Adam Schiff of California.

Congressman, thanks very much for joining us.

He was captured alive. How key could he be to U.S. intelligence? How confident are you he will provide information, rather than simply remaining silent?

REP. ADAM SCHIFF (D), CALIFORNIA: Well, I'm very hopeful that he will. And I think our experience has been pretty good in terms of the suspects that are in terrorism cases that are captured often do cooperate. They do talk.

So I would be surprised, although it's certainly possible he clams up. I would be surprised if we don't get some very good information. There is no one alive that can probably shed more insights into how this plot came about, how it was executed, precisely what involvement you may have had back in Raqqa, Syria, in the organization of this plot or the financing of it. So we stand to learn a great deal.

And France gets to bring to justice one of the terrible mass killers of our time.

BLITZER: If the French or the Belgian authorities manage to get him to talk, do you believe that would help thwart future attacks, potential ISIS attacks here in the United States?

SCHIFF: Well, it certainly will give us a lot of insights in how these external operations work, how they work logistically, how they're funded, what kind of targets that ISIS is putting their priority on.

He may have information about plotting in the United States, but we will certainly gain insights that will help us in combating attacks like in Paris. I can't say definitively that it will prevent an attack in the U.S. because the threat continues to evolve. But, nonetheless, there's probably no person alive that knows more about that particular plot in Paris. And we stand to gain incredibly valuable intelligence from him.

BLITZER: Will he be questioned by U.S. interrogators as well?

SCHIFF: That's a good question.

I would imagine that U.S. investigators will be able to participate in some degree. They may not be in the room while the questioning is happening, but often they allowed to provide questions that can be asked. But it's certainly possible that they could be present. And I fully imagine that the French authorities and the Belgian authorities will share with us the intelligence that they gather.

We will also help them to prepare their interrogation of this suspect by sharing information that we have about the plotters. So, this will be a combined effort.

BLITZER: How good is the intelligence cooperation that the United States has with Belgium and France?

SCHIFF: I think it's very good.

There are always ways to improve the relationship and improve the flow of information. I know there have been probably more frictions between the French and the Belgians than between either of them and the United States. But, nonetheless, the flow of information can always improve.

The biggest challenge, I think, frankly, given the continuing threats that we see in Belgium and France and Germany and elsewhere in Europe, is to break down the barriers to the flow of good information throughout Europe about who is where, who is involved in what, what foreign fighters have returned.

There's a real need. If they are going to continue to have this Schengen zone where people can move quite freely, they are going to have to have information move even more freely.

BLITZER: Are there others still at large, do you believe, based on all the information you have? And you are the ranking member of the Intelligence Committee. You are well-briefed. Others still at large in connection with Abdeslam, as far as the Paris terror attacks are concerned?

SCHIFF: I think it certainly appears there are others involved, in the sense of people that gave them shelter, people that may have provided logistical or other help.

I don't know that there's information that they were more than 10 of the people who actually participated in the attacks. He may very well be the last attacker, but I think there certainly are people that fled, I guess, the scene of one of the efforts yesterday in Belgium. So there are others that were, at a minimum, I think, involved in sheltering some of the people responsible.

[18:20:04]

BLITZER: Based on everything you know, Congressman, was this simply an ISIS-inspired terror attack in Paris or an ISIS-directed attack? In other words, did it go all the way up to Abu Bakr al-Baghdadi, the leader of ISIS?

SCHIFF: I suspect -- and this is one of the reasons, frankly, it will be so important to interrogate Abdeslam. I suspect that ISIS central gives general direction to these European

plotters, may help suggest targets to them, but then they have varying degrees of autonomy once they get into Europe. So, I wouldn't be surprised if they got funding and other logistical help, but once in Europe, they were able to choose very specific targets, they were able to figure out, OK, where would they get the vehicles? Where would they stay? How would they communicate with each other, using some of the operational security that maybe they got from ISIS central and from their how-to guides.

But I think there's probably a degree of autonomy in all of these Western attacks.

BLITZER: It took four months to apprehend Abdeslam. Why did it take so long? Because a lot of people are wondering if it's very worrisome that he was able to cross borders from France into Belgium to hide for months at a time.

SCHIFF: Well, it's a good question, and, indeed, Abdeslam apparently was stopped at the border shortly after the Paris attack, but he wasn't known to be an attacker at that point.

So, again, part of it is the flow of information, how long that takes. He also may have been holed up in this Molenbeek neighborhood that I visited just a couple of months ago and not ventured out very much, not exposed himself, so that even his immediate neighbors may not have known that he was in that particular building.

We will know a lot more, I think, once the interrogation is done. But if you are trying to hide and you stay low and you don't use electronics, it's very easy to avoid detection, even when police are in your very neighborhood and looking.

BLITZER: The other breaking political news we're following, a dramatic new attempt by Mitt Romney to prevent Donald Trump from winning the Republican presidential nomination and a blistering attack on what he calls Trumpism.

And Bernie Sanders walking out of a TV interview suddenly. What was the question about his wife that apparently outraged the Democratic candidate?

(COMMERCIAL BREAK)

[18:27:06]

BLITZER: More now on the breaking political news, Mitt Romney now saying he's voting for Ted Cruz and encouraging others to do the same to prevent Donald Trump from winning the GOP presidential nomination. CNN political reporter Sara Murray is joining us now.

What else is going on, Sara? This is pretty dramatic.

SARA MURRAY, CNN NATIONAL POLITICAL CORRESPONDENT: It is very dramatic, Wolf.

The statement that Mitt Romney put out is dramatic, and Ted Cruz is already using this as an indication that Republicans are lining up behind him, using it to try to nudge John Kasich to step aside.

But Kasich and Cruz both say they are going to fight to the convention and Donald Trump is saying that spells pandemonium.

(BEGIN VIDEOTAPE)

MURRAY (voice-over): Tonight, Mitt Romney is throwing his support behind Ted Cruz, taking to social media to say he will cast a ballot for Cruz in Utah in an effort to defeat Donald Trump, posting this on Facebook: "The only path that remains to nominate a Republican rather than Mr. Trump is to have an open convention. At this stage, the only way we can reach an open convention is for Senator Cruz to be successful in as many of the remaining nominating elections as possible."

Trump swiftly retaliating on Twitter, saying: "Failed presidential candidate Mitt Romney, the man who choked and let us all down, is now endorsing lying Ted Cruz. This is good for me" -- all of this as Cruz tries to clear the path for a one-on-one fight with Trump, repeating his calls for John Kasich to step aside.

SEN. TED CRUZ (R-TX), PRESIDENTIAL CANDIDATE: A vote for John Kasich is a vote for Donald Trump. If Kasich manages to pull enough votes in Utah to pull me below 50 percent, the effect of John Kasich will be giving Donald Trump 20 more delegates, which I think would be a big, big mistake.

GOV. JOHN KASICH (R-OH), PRESIDENTIAL CANDIDATE: Mitt is fine. This is his view. And he's entitled to it. And, frankly, I don't think anybody is going to have enough delegates to get to the convention.

DONALD TRUMP (R), PRESIDENTIAL CANDIDATE: We're way ahead of everybody. I don't think you can say that we don't get it automatically. I think you would have riots. I'm representing a tremendous, many, many millions of people.

MURRAY: His rivals panning the comment as more reckless talk from the GOP front-runner.

KASICH: To even imply that there could be violence if he doesn't get his way, he's not running for the presidency of the WWE. He's running for president of the United States. And this kind of language is an outrage.

MURRAY: Kasich's allies are highlighting the violence around Trump's events and casting the Ohio governor as the only candidate fit to take on Hillary Clinton.

NARRATOR: There was a time presidents were honorable, trustworthy. What's happened?

MURRAY: Meanwhile, Trump is facing threats beyond the political realm.

UNIDENTIFIED MALE: Your inconsistent and hateful campaign.

MURRAY: Members of the hacking collective Anonymous taking aim at the GOP front-runner.

[18:30:05] UNIDENTIFIED MALE: This is not a warning. This is a declaration of total war. Operation Trump engaged.

MURRAY: ... posting online what they allege to be Trump's Social Security and cell phone number. Trump's campaign says officials are seeking the arrest of the people behind it.

In a separate incident, one of Trump's sons, Eric Trump, received a threatening note containing a suspicious powder. While it appears to be lemonade mix, authorities are investigating.

(END VIDEOTAPE)

MURRAY: Now, Wolf, we're expecting Donald Trump here in Salt Lake City in just a couple of hours. This is not a state where he's favored to win, though. So Mitt Romney getting in on the race could actually be a blow more to Kasich than it could be to Trump.

We're already seeing the Kasich campaign hit back on that. They're up with a new ad on the Internet that shows Mitt Romney campaigning for Kasich in Ohio and complementing the Ohio governor, clearly trying to undo some of that damage for Mitt Romney coming out and saying he's voting for Ted Cruz -- Wolf.

Mark, the "stop Trump" campaign, Mitt Romney writing today, "Through the calculated, statements of its leader, Trumpism has become associated with racism, misogyny, bigotry, xenophobia, vulgarity, most recently, threats and violence. I am repulsed by each and every one of these."

But is it too late?

MARK PRESTON, CNN POLITICS EXECUTIVE EDITOR: It very well may be too late. And you know, one of the things that I've heard time and time again is that the reason why it's too late is that the folks that could have funded it and the folks that could have perhaps stopped Donald Trump saw Ted Cruz as the ultimate beneficiary. And two months ago, they didn't like that at all. They thought that Marco Rubio was their candidate. They thought that Cruz would be the person who could benefit the most from it. That's why they didn't get in on it.

But at this point right now, it might be -- it might be too late for them to get involved. It might not be too late to stop Trump from getting the 1,237 delegates he needs to get to Cleveland.

BLITZER: It's interesting that Romney also said he likes John Kasich, the Ohio governor, but basically said a vote for him is a waste. It would only help Trump. Your reaction?

JEFF ZELENY, CNN SENIOR WASHINGTON CORRESPONDENT: I was more struck by the language that he used in his statement here. I mean, this is the former Republican nominee. I mean, only four years ago here.

So this whole revolt in the party is now becoming sort of a side show.

Salt Lake City and Utah may be one of the places where Mitt Romney's words actually may matter. But so he may be able to mathematically block Trump from getting those delegates, but we'll see. This will be the ultimate test if Mitt Romney has any weight any more at all.

But what Mark said earlier hits the nail on the head. Ted Cruz was not -- was never seen as an acceptable alternative. Many establishment Republicans, you know, used to be equally concerned or more so about Ted Cruz. So that just shows you what point we've come to. I'm not sure that it matters.

BLITZER: Well, Ron, what do you think? He's calling for an open convention. What happens if Donald Trump fails to secure the majority, the 1,237 delegates he needs to win the nomination on the first round?

RON BROWNSTEIN, CNN SENIOR POLITICAL ANALYST: If he does not get the majority in the first round, we have a contested convention. A multi- ballot convention. And to give you a sense of how big a leap into the unknown that is the Republicans, the last time they had that, Wolf, was 1948. It was the first convention where any portion of the convention was covered by television. NBC and Life Magazine, of all people, covered it for part of the convention. And the combatants for the nomination were Tom Dewey, Robert Taft and Harold Stassen.

So when you're talking about Harold Stassen and Tom Dewey as the last time that Republicans had been in precisely this situation, it gives you a sense of just how extraordinary a moment this is, particularly if Trump continues in this pattern, where he is well ahead of any of his rivals but still a plurality front-runner facing resistance from big portions of the party, not only the leadership but portions of the electorate that does not seem to be dissolving, even as he advances toward that nomination.

BLITZER: Rebecca, how big of a deal is it for the immediate past Republican presidential nominee to be calling for an open convention, strategic voting at this sensitive time?

REBECCA BERG, REAL CLEAR POLITICS: It's a huge deal for the reasons that Jeff mentioned, because of the language that he is using to talk about the current front-runner. But also because, look at what this means for John Kasich's candidacy in the immediate future. The whole case that John Kasich can make at this point for still being in this race is that his candidacy helps Republicans get to an open convention.

If more Republicans start making the argument that Mitt Romney is making, that it actually would hurt Republicans' chances at making an open convention for John Kasich to stay in the race, he's going to have a very, very big existential crisis on his hands.

BLITZER: Donald Trump, Jeff, tweeted this, reacting to the Romney statement: "Failed presidential candidate Mitt Romney, the man who choked and let us all down, is now endorsing Lyin' Ted Cruz. This is good for me."

Is he right?

[18:35:02] ZELENY: He tweeted that among many other things. He was very busy on Twitter this afternoon. We'll see if he's right or not. I think Utah may be the one place where he's not right. But going forward, I just don't think that Mitt Romney's voice -- anyone who agrees with him already agrees with him and is not voting for Trump anyway here. So...

BERG: Although I would argue among GOP leaders and elites, it does matter that he is suddenly pointing out that Ted Cruz is a practical option.

ZELENY: Most people were already there. Lindsey Graham kind of, you know, was holding his nose yesterday during the same thing. I mean, the options are running out.

BERG: Look at Mitch McConnell. Look at some of these other senators. There's a long way to go.

BLITZER: Mark, you know that there are a lot of Republicans out there that don't want to vote for Donald Trump. But they say they don't even want -- they don't want Ted Cruz even more than they don't want -- they don't like Ted Cruz either.

PRESTON: Well, the situation we're in is so bizarre. I mean, this is -- we're in Bizarro-land right now. Because if you go back like eight, nine weeks ago to Jeff's point earlier, there was talk about, like, maybe Ted. Maybe Donald Trump would be better than Ted Cruz, because the devil we know is better than the devil we know better. And they all thought that Ted Cruz was somebody that, you know, as I was told by someone the other day, Wolf, just to capitalize this.

With Ted Cruz, nobody was upset about his ideology, about being a hard-core conservative. They thought that he just turned their backs on him in the Capitol, that he wasn't a team player, that he tried to shut down the government and he did things that hurt the Republican Party. That's why they were so upset at Ted Cruz.

BLITZER: Ron, you wanted to weigh in?

BROWNSTEIN: Well, I say, they also thought that Ted Cruz was a likely loser in November. But I think one of the reasons why you're seeing this shift in emphasis is because of the short-term and long-term risks.

It's entirely possible that Donald Trump is a more competitive candidate in the general election in 2016 than Ted Cruz. But if Ted Cruz runs and loses as the nominee, he runs and loses and he goes away. The risk with Donald Trump, underscored by these remarkable words from Mitt Romney, which are probably unprecedented for a former nominee to talk about a potential future nominee in those terms. The risk of Donald Trump is lastingly rebranding the Republican Party.

When you're talking about describing the nominee as xenophobic, racist, bigoted and misogynistic, that is the danger for the Republican Party, particularly as we're going through these historic demographic changes with this enormously diverse millennial generation. Will he stamp the Republican Party as a party of white racial backlash, whatever happens in this election, even if he can squeeze out enough white support to win.

And I think that is the real risk that many Republicans are focused on. That he's a much longer term threat to the viability of the party than Ted Cruz.

BLITZER: All right. Everyone stand by. We have more to assess. More information coming in.

Important programming note to our viewers, as well. Donald Trump will join me here in THE SITUATION ROOM on Monday, 5 p.m. Eastern. You'll want to see the interview. We'll be right back.

(COMMERCIAL BREAK)

[18:42:32] BLITZER: Bernie Sanders and Hillary Clinton are increasingly turning their attention to Donald Trump as he moves closer to securing the Republican presidential nomination. And concern about the millionaire businessman's controversial campaign extends all the way to the White House.

Our senior political correspondent, Brianna Keilar, is joining us with details. Brianna, no one is dismissing Trump at this point, are they?

BRIANNA KEILAR, CNN SENIOR POLITICAL CORRESPONDENT: No. Including President Obama. Publicly he's tried to remain neutral about which Democrat he supports. But he's giving us a bit of a preview about how he will rally Democrats in the general election.

(BEGIN VIDEOTAPE)

KEILAR: President Obama weighing in on the 2016 race as he looks to protect his legacy, telling NPR today he thinks the Republican-led Senate's refusal to hold hearings on his Supreme Court nominee will motivate Democratic voters.

BARACK OBAMA, PRESIDENT OF THE UNITED STATES: In part because of the circus that has been the presidential campaign season so far.

KEILAR: Obama, once dismissive of Donald Trump in January...

OBAMA: Talk to me if he wins.

KEILAR: ... and February...

OBAMA: I continue to believe Mr. Trump will not be president. And the reason is because I have a lot of faith in the American people. It's not hosting a talk show or a reality show.

KEILAR: Now with Trump the clear front-runner in the Republican field, the president is sounding a warning about the heightened rhetoric on the campaign trail.

OBAMA: The longer that we allow the political rhetoric of late to continue and the longer that we tacitly accept it, we create a permission structure that allows the animosity in one corner of our politics to infect our broader society.

KEILAR: Obama has met with both Hillary Clinton and Bernie Sanders this primary season, speaking especially highly of his former secretary of state. But the White House is pushing back on a "New York Times" report that Obama told Democratic donors to rally behind Clinton.

JOSH EARNEST, WHITE HOUSE PRESS SECRETARY: The president did not indicate a preference in the race.

KEILAR: But Obama has made a pick. Press Secretary Josh Earnest says he's just keeping it to himself.

EARNEST: I did not say that he couldn't make up his mind. The president's cast a ballot.

SEN. BERNIE SANDERS (D-VT), PRESIDENTIAL CANDIDATE: What this campaign is about is urging the American people to think outside of the box.

[18:45:01] KEILAR (voice-over): Sanders is trailing Clinton considerably in the delegate count. His patience wearing thin Thursday as he abruptly cut off an interview with a Phoenix television station.

(END VIDEOTAPE)

KEILAR: And in a rather unusual move, Bernie Sanders who is the only Jewish candidate in the race will not be addressing the AIPAC conference, the pro-Israeli lobby on Monday, Wolf. The only candidate who isn't doing that, clearly trying to concentrate on the western states where he thinks he has an edge over Hillary Clinton.

Rebecca, let's talk a little bit about Donald Trump. He tweeted this about Hillary Clinton. He's been tweeting a lot about her lately, "Who should star in a reboot of 'Liar, Liar", Hillary Clinton or Ted Cruz? Let me know."

Obviously, he's beginning to think ahead, maybe ahead of the Republican nomination. But he's clearly devoting more of his attention to Hillary Clinton right now.

REBECCA BERG, NATIONAL POLITICAL REPORTER, REAL CLEAR POLITICS: Clearly. And clearly, it's going to be an elevated discussion we're going to have in the general election if Donald Trump is the nominee against Hillary Clinton, but it's definitely a deliberate pivot for him because he sees this delegate lead at this point. He wants to stoke this idea of himself as the likely Republican nominee, if not the prohibitive front-runner to become the Republican nominee.

The best way to do that is by skipping the debate this week to do another event of his choice and just start talking about Hillary Clinton, measuring himself instead to her as opposed to his Republican rivals.

BLITZER: You've seen all these reports that the leadership would like Bernie Sanders to drop out so Hillary Clinton could focus all of her resources, all of her attention on a general election. Is that going to happen?

MARK PRESTON, CNN POLITICS EXECUTIVE EDITOR: No, and it shouldn't happen. It shouldn't be the leadership that tells Bernie Sanders it's time to get out of the race. As we just show on those pictures right now when he goes out and does these rallies, he's getting 3,000, 4,000, 5,000 people that are coming out for him.

We only need to go back to 2007 and 2008 where we saw the Barack Obama political machine stay operational and not dormant because she was in a tough battle with Hillary Clinton through about May and it stayed up until she got out in June. That means he was a stronger candidate going into the general election. And quite frankly, this is what gets people so upset about Washington, is the insiders telling the voters that they know what's good for them.

Let Bernie Sanders stay in. And that's why Hillary Clinton is very smart not to try to tell him to get out.

BLITZER: Ron, the Sanders campaign, they're going to try to secure more votes out in the west now. Will they get enough delegates to make it competitive against Hillary Clinton?

RON BROWNSTEIN, CNN SENIOR POLITICAL ANALYST: The short answer is no. I mean, they could do well in some of these western states. Many of them are caucuses, they're smaller turnout. They're predominantly white electorates, where he has been much more competitive, although, actually she's won white voters in more states than he has, which is a little known fact.

But the fundamental challenge he faces remains, which is on the Democratic side, all of the big states are diverse states. I mean, every single one. Every state with a big delegate trove tends to be diverse. So, yes, Washington state, Idaho, Utah, Oregon maybe, Vermont, obviously. You can compete there.

But unless you can improve your performance against African-Americans, particularly, but also more consistently among Latinos, when you look at the big states on the board out there, whether it's California, New York or New Jersey, it gets much more difficult for Bernie Sanders. And in that -- in that competition, you know, I think there's no question about whether you trade a California for a Utah.

BLITZER: You've seen these reports that major pro-Hillary Clinton super PAC has now decided to not spend any more money in this preliminary round but to save the money for a general election. They assume, I assume, that Hillary Clinton has it locked up.

JEFF ZELENY, CNN SENIOR WASHINGTON CORRESPONDENT: They do. And frankly it would agitate supporters of Bernie Sanders. And there are more than 6 million reasons not to do that because that's the number of votes he's gotten so far. He's going to have millions more by the time this process is over. That's one reason --

BLITZER: She's going to need that support of that base.

ZELENY: She is going to. And they want to start trying to define Donald Trump. It's one thing the Republican establishment could not do.

But that doesn't mean that he's been defined in a general election yet. He's been defined to a primary electorate. The Democrats believe that there's an opportunity here. And Mitt Romney's statement today, we talked about earlier, I guarantee that is going to be in an ad from the Democrat. It's going to be out to every independence voter, every swing voter, every suburban voter. That is what could ultimately hurt Donald Trump in the general election.

BLITZER: It could be more effective in the general election than primary.

ZELENY: Why waste your money now on Bernie Sanders? It's a total waste of money.

BLITZER: Go ahead, Ron.

ZELENY: Just to amplify what Jeff is saying. I mean, the ad, the Our Principles PAC has put up of women reading Donald Trump quotes -- I mean, you can run that ad in the general election and without changing a word in the suburbs of Denver or northern Virginia or I-4 corridor in Florida.

You could see that exact ad and it would be probably much more effective in a general election context than in a primary context.

BLITZER: Very quickly, Rebecca, you saw in Brianna Keilar's report, at the end of that interview he was having, Bernie Sanders, he just walked out, took off the microphone and walked out. What did that say to you?

BERG: He did. Well, one of the misconceptions that I have seen about this is that he walked off in response to a question about his wife.

[18:50:00] In fact, he walked off after a question about whether he would be Hillary Clinton's vice president, a question he's answered many times before. I think really he was fed up and this was the impression of the reporter interviewing him. He was just fed up that it took too much time and he was over it.

BLITZER: All right. Guys, stand by, because we've got more coming up.

Also, I want to give you an update on the Flint water crisis. The death toll from an outbreak of Legionnaire's disease coincided with the emergency has risen now to 10. But so far, there's no proven link, officials say, about one third of the patients received Flint water in their homes.

The Michigan Governor Rick Snyder is facing calls to resign over the crisis. He told a congressional hearing he was misled about the severity.

To find out by the way how you can help the victims of Flint, visit CNN.com/impact and you'll be able to impact your world.

Much more news right after this.

(COMMERCIAL BREAK)

[18:55:32] BLITZER: This Sunday, President Obama will become the first sitting president of the United States in almost a century to visit Cuba, marking the ongoing normalization of relations between Washington and Havana.

Sunday night, "THE WONDER LIST WITH BILL WEIR" returns to CNN with a season premiere exploring Cuba at a crossroads.

(BEGIN VIDEO CLIP)

BILL WEIR, THE WONDER LIST: It looks like a trendy boutique you might see in Soho or Melrose District of Los Angeles. And then right across the street, you have people raising chickens on their balcony.

How is life in Havana these days?

UNIDENTIFIED MALE: It's really hard, man.

WEIR: It's hard?

UNIDENTIFIED MALE: Yes. Some people think change. I hope so.

WEIR: You hope so. You don't think so?

UNIDENTIFIED MALE: Maybe change for business, for government.

WEIR: Uh-huh.

UNIDENTIFIED MALE: But for the people, I don't know. More young people is better.

WEIR: Young people in government, yes.

UNIDENTIFIED MALE: Yes, (INAUDIBLE) revolution.

WEIR: New ideas.

UNIDENTIFIED MALE: Yes, new idea, we need that. Maybe a few years, good.

WEIR: Really?

UNIDENTIFIED MALE: Yes, man.

WEIR (voice-over): I came here expecting to find that sentiment everywhere, but to my surprise, so many seemed proud of the Cuban system, warts and all.

(END VIDEO CLIP)

BLITZER: Bill Weir joins us now live.

Bill, what were the biggest surprises on your trip to Cuba?

WEIR: Well, it was -- it was -- I was taken aback by a lot of excitement for Americans. You know, they've been our unknown neighbors for so long, so much suspension going both ways. But an incredibly open hearted, warm, generous, curious folks, but it was also tinged with this apprehension about keeping their Cuban soul, not seeing American corporations, American corporations coming in and sort of bulldoze what is precious to them, and just how broken the country is. Water, power, communications really is stuck in the '50s just like those old classic hunks of Detroit steel you see rolling out there.

But I think it's going to take a lot longer. I expected it, as many people do, to turn into Cancun now that the floodgates are open. I think it's going to take a lot longer than we expect and we'll explain why in the show Sunday night. BLITZER: Did you have government minders with you as you were roaming around Havana and elsewhere?

WEIR: No, on the contrary. They said go everywhere. Not just the pretty places. We want you to go into the more depressed places, talk, see how life truly is for the average Cuban. And I wondered how guarded they would be.

But as one gentleman told me on camera, he told me an old Cuban joke that would have gotten him thrown in prison just a few years ago, which is, you know what the three greatest success of the revolution were? Medicines, and the arts, and sports. But the greatest failures -- breakfast, lunch, and dinner.

There was this sort of old jaundiced eye towards their own government. Some, you know, voiced a real affection for the Castros and the regime, but to a person, all had criticism, all had harsher words than I ever expected to hear in a place like that.

BLITZER: Yes, the timing of this, the releases of the season premiere is amazing, coming at this historic moment in U.S.-Cuban relations and the visit of the president -- the first time in 88 years that an American president has visited.

Bill, we're looking forward to it. Nice beard, by the way. Glad you're following others' footsteps. Appreciate it very much.

WEIR: I'm chasing you, Wolf. You're my role model.

BLITZER: All right.

Here's the deal, you can see the season premiere of the CNN original series, "THE WONDER LIST WITH BILL WEIR", Sunday night, 10:00 p.m. Eastern. Important viewing.

And two other important programs to note for our viewers: this coming Monday, Donald Trump will join me here in THE SITUATION ROOM at 5:00 p.m. Eastern.

And at 8:00 p.m. Eastern, a CNN presidential primetime event, the final five presidential candidates all make their cases to the voters on the same night. Democrats and Republicans. The final five. Monday night at 8:00 p.m. Eastern, only here on CNN. Anderson Cooper and I will anchor that special three-hour program.

Thanks very much for watching. I'm Wolf Blitzer in THE SITUATION ROOM.